Electric switch



Feb. 18, 1941.

R. s. CRAIG ELEVCTRI C SWITCH Filed Oct. 7, 1937 2 Sheets-Sheet l Inventor .Jfobert 5. Craig R. S. CRAIG ELECTRIC SWITCH Feb. 18, 1941.

Filed Oct. '7, 1937 2 Shee ts-She'et 2 1i obert 6 Cra 2/ A113 Patented Feb. 18, 1941 UNITED; STATES assassin "PATENT OFFICE Claims. (01; 200-152) This invention relates to liquid flow switches and more particularly to mercury switches.

The prime object or this invention isto provide a liquid flow switch which in one operative posi- 5, tion will complete a first circuit, and when moved toward another operative position will complete I a second circuit before breaking the first circuit,

but when moved back toward its first position will break the second circuit before re-making the first circuit. 7

. Other objects and advantages will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawings.

In thedrawings, Figure 1 is a sectional view of one embodiment of the invention shown ina position in which one circuit is closed;-

Figure 2 is a sectional view of the switch of Figure Lin the position in which both circuits are closed; l

Figure 3 is a sectional view of the switch shown' in Figure 1 in the position in which the second circliit only is closed; Figure 4 is a sectional view of the switch shown in Figure 1 in open circuit positiom.

Figure 5 is a-sectional view ot another embodiment or'the invention'in' which one circuit is closed; a Figure 6 is a sectionalnview oi the switch own v in Figure 5 inwhich both circuits are cl d;

Figure 'l is a sectional view of the switch shown 'in Figure 5' in which a second circuit only is closed, and

Figure 84s a sectional view or the'switch shown I in Figure 5.i'n open circuit position.

In the embodiment of thefinvention shown in Figures 1 through a. like reference characters refer to the-same parts in the several views. The

switch'envelope. i0 is made oi glass'or other insulating material andis tubular in, form. The lower exterior surface or floor Ii '0! the envelope III is substantially straight for the greater part otits-length'. -The usual sealing-oil. tip "in this illustrative embodiment is located at one end of the envelope II and o the lower side thereof, thereby forming a depression it. on the inside or the tube. Electrodes ll, I! and- Ii extend into the tube, their inner; ends being positioned close to the bottom vsurface ll of the tube, d are suitably sealed into the glass envelope .at/l-I, ll and I9. External connections may be made to the outer'ends 20,21 and 22 or the electrodes by tame flexible leads (not shown') m sn the envelope I II is a globule of mercury 28 adapted to make contact with the various electrodes.

The operation oi this vdevice is illustrated in Figures .1 through 4. In Figure 1. the envelope ill is shown tipped so that the end in which the 5 sealing-oil tip i2 1W4 is the lower, and therefore the mercury as run to this end of; the tube. Electrode I4 is located immediately above the sealing-oil tip I! while electrode l5- is so formed that one end of it also extends to 10 this end or the tube.. Theglobule of mercury 23 is large enoughso that in this osition of the electrodes.

'As the envelope is tipped clockwise from the position shown in'Figure l to a position slightly past horizontal, the mercury 23 will assume the position'shown in Figure 2 in which the mercury bridges allthree electrodes ,1! and i6. Them mercury in this position 0! the tube is somewhat longer longitudinally or the tube than it would be it part or it were not lodged in epression l3 formed by the sealing-of! tip l2. I e mercury which lies within depression l3 adheres thereto; 25 and although the .envelope lsso 'tippedthat there is va, slight gradient along itslower surface 'll awayfrom depression i3,'the surface tension of the mercury is great enough to hold the portion attempting to move away from depression l8 to, 30, the part lodged therein. Thus by suitably pro'-' portioning the shape 01' tube III, the position of the electrodes and the amount oLmercury withinthe tube, all three electrodes are bridged at once. I Tipping the envelope Ill further in a clockwise 35' direction will establish a gradient along the bottom ii of the envelope and away from the depression ll that will be great enough to overcome "the suriacetension of the mercury and it'wili separate into two parts as shown in Figure- 34 Asmall portion of the mercury 23a will remain lodged in depression I! while the greater-part of the mercury 23b will ilow, to the other end of the 'Asthe-enveldpe I0 is otatedcounter-clockwise' irom the position shown in- Figure ,3 and when the "lower internal surface ll of the envelope becomes horizontal the mercury willassume the 50 --podtion shown in Figure 4. The mercury 23b has left electrode it but, has not yet reached electrode i4 and the portion-of mercury 23a lying'wlthin the depression i3. f'Dueto the vfact that there is now no tension on mercuryjlb', it

will be considerably 'shorter than it was in the position of the tube shown in Figure 2 and short enough so that it bridges no electrodes. Further tipping in a counter-clockwise direction will bring the various parts backinto the position shown in Figure 1.

A second embodiment of the invention is shown in Figures 5 through 8. This embodiment accomplishes the same result as the previously described embodiment but in a somewhat different manner. Reference characters employed in Figure 5 apply to Figures 6, 'Z and 8.

An envelope of glass or other insulating mate- -rial is illustrated generally at 30. This envelope is tubular in form and includes a substantially straight lower internal surface or fioor 3| and a conventional sealing-off tip 32 at one end of the envelope. The envelope surface is indented as at 33 forming a raised portion or obstacle 34 in the lower internal surface 3|. Electrode 35 is positioned between one end of the envelope and the raised portion 34. Electrode 36 extends substantially parallel to the bottom 3| of envelope 30 from a point close to the raised portion 34 to a point fairly close to the other end of the tube. Electrode 31 extends within the tube toa point close to the bottom 3| of the envelope 30 and in the end thereof opposite they raised portion 34. Electrodes 35, 36 and 31 are suitably sealed in the-envelope 30 as at 38, 39 and 40.- Flexible lead wires, not shown, associated with external .end of electrode 36. 'Asthe envelope is tipped in a clockwise direction from the position shown in Figure 5 until the bottom surface 3| of the envelope is substantially horizontal, the mercury 44 will assume the position shown in Figure 6 in which it bridges electrodes 35, 36 and 3| j. The raised portion 34 is so proportioned to the shape of the envelope, the amount of mercury and position of the electrodes that while there, is a tendency to sheer the mercury into'two'parts at 34,

the surface tension of the mercury is sufilcient to maintain contact between all the electrodes. Further clockwise tipping of the envelope will bring it to the position shown in Figure 'l, in which-contact is broken between electrodes 35 and 36, the mercury all having run to the other end of the envelope making contact only be-- tween electrodes 36 and 31. Tipping the envelope counter-clockwise from the position shown 'in Figure '7 until the lower internal surface 3| of ther counter-clockwise tipping of the tube will cause the mercury 44 to flow over raised portion 34 and again complete; the circuit between electrodes 35 and 36.

It will be seen that in both illustrated embodiments of the invention that by causing the mercury to be shorter when flowing in one direction than in the other, a single-pole double-throw switch has been provided in which the two cirbeing straight except for an irregularity near one cults overlap in one switching operation but not in the reverse switching operation.

Various other materials and arrangements 0 the parts could easily be employed, and it is desired that the scope of the invention be deter- 6 mined only by the appended claims and prior art.

I claim as my invention:

1. In an electrical switching mechanism, incombination, an elongated container having first and second ends tiltable to a first position in which the first end is lower and to a second position in which the second end is lower, electrodes in the first end of the container for controlling a first circuit, electrodes in the second end of the container for controlling a second circuit, a body of mercury" in the container for bridging the electrodes in the first end of the container when the container is in the first position and for bridging theelectrodes in the second end of the container when the container is in the second position, said container having a floor provided with an irregularity near one end the remainder. of the floor being so formed as to permit the fiow of mercury with equal facility as the tube -is tilted in either direction, the mercury being of sufllcient volume to bridge the electrodes in the second end of the container before unbridging the electrodes in the first end of the container as the container is tilted from-the first to the second position and -for causing the mercury to .unbridge the electrodes in the second end of the container before bridging the electrodes in the first end of the container as the container is tilted from the second to the first position.

2. In an electrical switchingmechanism, in

combination, an elongated container having first and second ends tiltable to a first position in which the first end is lower and to a second position in which the second end is lower, electrodes in the first end of the container for controlling a first circuit, electrodes in the second end of the container for controlling a second circult, a body of mercury in the container for j bridging the electrodes in the first end of the container when the container is in the first position and for bridging the electrodes in the second end of the container when the container is in the second .position, the bottom of said, container being' straight except for an irregularity, said irregularity in the bottom of said container af-. fecting the normal length of the mercury as the container is tilted in ,one direction, said irregularity having substantiallyno eifect on the normal length of said body of mercury, as said con-' tainer is tilted in the opposite direction, said irregularity, in conjunction with the relative size of the container and volume of mercury, operating to cause said circuits to be overlappingly controlled as the container is tilted in a first direction and non-overlappingly controlled as said container is tilted in a second direction.

3., In an electrical switching mechanism, in

combination, an elongated container having first and second ends tiltable to a first position in which the first end is lower and to a second position in which 'the second end is lower, electrodes inth'e first endfor controlling a first circult, electrodes in the second end for controlling a second circuit, the bottom of said container end thereof, a body of mercury in the container comprising a first portion which is continuously retained by said irregularity in contact with one oi the electrodes in the first end of the container 1 and a second portion movable between the first I and second ends of the container for bridging the electrodes in the first end of the'contai-ner when the container is in the first position and for bridging the electrodes in the second end of the container when the container is in the second position, the volume of said second portion being such that normally when the container is horizontal the second portion will be of insufilcient length to bridge all the electrodes, but when the second portion is united with the first portion and the container is tilted so that there is a slight gradient toward the second end 01' the container the mercury will he of a length sumcient to bridge all the electrodes.

4. In an electrical switching mechanism, in combination, a cylindrical container having first and second ends. tiltab'le to a first position in which the first end is lower and to a second posi- 1 tion in which the second end is lower the bottom of said container being straight except for an obstruction in the first end thereof, electrodes in the first end of the container for controlling a first circuit, electrodes in the second end of the container for controlling a second circuit, a body of mercury in the container for bridging the electrodes in the first end of the container when the container isin the first position and for bridging the electrodes in the second end of the container when the container is in t the electrodes in the second end of the container before unbridging the electrodes in the first end of the container as the container is tilted from the first position to the second position, said ohsecond position and being of a volume sufiicient to bridge stmction in the first end of the container having a height sufllcient to restrain the movement of i the mercury toward the first end of the container "I when the container is tilted from the second toward the first position until the mercury unbridges the electrodes in the second end of the p 1 container.

5. In an electrical switching mechanism, m

combination, a cylindrical container having first and second endstiltable to a first position in 1b which the first end is lower and to a second posi tion in which the second end islower, a well in the first end of the container formed by the seal-f ing-ofi tip of the container, electrodes in the first endfor controlling a first circuit, electrodes in the second end for controlling a second circuit,

a body of mercuryin the container comprisinga.

first portionwhich is continuously retained by' the well and a second portion movable between.

the first and second ends of the container for bridging theelectrodes in the first end of the v container when the container is in the firstposition and for bridging the electrodes in the second end of the container when the container is inthej second position, the volume of said second portion of mercury being such that when the cons tainer is horizontal and is'being tilted from the 

